1. Field of the Invention
The present invention relates to a method for producing a Group III nitride-based compound semiconductor having a so-called wurtzite structure. More particularly, the present invention relates to a method for producing, through epitaxial growth, a Group III nitride-based compound semiconductor having an M-plane main surface. The present invention also relates to a Group III nitride-based compound semiconductor device including a wafer having an M-plane main surface, and a layer having an M-plane main surface. In a wurtzite structure (i.e., hexagonal crystal structure), M-plane is represented by a Miller index of (1-100). As used herein, the bar line which is conventionally provided above a component of a Miller index is denoted by the symbol provided immediately before the component.
As used herein, “Group III nitride-based compound semiconductor” encompasses a semiconductor represented by the formula AlxGayIn1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1); such a semiconductor containing a predetermined element so as to attain, for example, an n-type/p-type conduction; and such a semiconductor in which a portion of a Group III element is substituted by B or Tl, or a portion of the Group V element is substituted by P, As, Sb, or Bi.
2. Background Art
Group III nitride-based compound semiconductor light-emitting devices have been widely used, and many attempts have been made to improve characteristics of the devices. In general, a Group III nitride-based compound semiconductor light-emitting device is produced through epitaxial growth of a Group III nitride-based compound semiconductor on a substrate made of a material different from Group III nitride-based compound semiconductor (hereinafter the substrate may be referred to as a “hetero-substrate”); for example, a sapphire substrate. In a most common epitaxial growth process, a Group III nitride-based compound semiconductor is grown so that the thickness direction of the semiconductor is along the c-axis, and the semiconductor has a C-plane main surface.
As has been known, when, in a Group III nitride-based compound semiconductor light-emitting device, for example, layers having a multiple quantum well structure are stacked in a c-axis direction (i.e., the interface between stacked layers is parallel to C-plane), a piezoelectric field is generated by strain in the light-emitting device, and quantum efficiency is reduced. Generation of such a piezoelectric field attributed to internal strain is also undesirable in the case of formation of a device other than a light-emitting device (e.g., HEMT).
In view of the foregoing, attempts have been made to develop a technique for epitaxially growing a Group III nitride-based compound semiconductor so that the thickness direction of the semiconductor is not along the c-axis. Japanese Patent Application Laid-Open (kokai) No. 2006-036561 (filed by the present applicant) discloses a technique for preventing growth of a crystal in an undesirable growth axis direction through formation of a mask.